Associate Professor Anthony Kiem

Understanding interactions between surface water (SW) and groundwater (GW) is challenging because of the lack of information available and the complexity of the processes involved. In this paper, SW-GW interactions are simulated using numerical modelling integrated with insights from water isotopes. Isotope analysis can be used to (i) determine the relative contribution from different sources of water into aquifer recharge and (ii) identify areas with high SW-GW interactions. The results, for the Shiraz catchment in Iran, show that (i) SWAT-MODFLOW has better performance than stand-alone SWAT (R2 improvement from 0.50 to 0.54) and (ii) SWAT-MODFLOW calibrated with insights from isotope data (SWAT-MODFLOW-ISO) has significantly better performance than SWAT-MODFLOW (R2 improvement from 0.54 to 0.68 and RMSE reduction from 1.67 to 1.33). This demonstrates that insights into SW-GW interactions that are revealed by isotopes can be used to improve hydrological modelling performance.

Drought is a global threat to public health. Increasingly, the impact of drought on mental health and wellbeing is being recognized. This paper investigates the relationship between drought and well-being to determine which drought indices most effectively capture well-being outcomes. A thorough understanding of the relationship between drought and well-being must consider the (i) three aspects of drought (duration, frequency, and magnitude); (ii) different types of drought (meteorological, agricultural, etc.); and (iii) the individual context of specific locations, communities, and sectors. For this reason, we used a variety of drought types, drought indices, and time windows to identify the thresholds for wet and dry epochs that enhance and suppress impacts to well-being. Four postcodes in New South Wales (NSW), Australia, are used as case studies in the analysis to highlight the spatial variability in the relationship between drought and well-being. The results demonstrate that the relationship between drought indices and well-being outcomes differs temporally, spatially, and according to drought type. This paper objectively tests the relationship between commonly used drought indices and wellbeing outcomes to establish whether current methods of quantifying drought effectively capture well-being outcomes. For funding, community programs, and interventions to result in successful adaptation, it is essential to critically choose which drought index, time window, and well-being outcome to use in empirical studies. The uncertainties associated with these relationships must be accounted for, and it must also be realized that results will differ on the basis of these decisions.

The Eastern Seaboard of Australia (ESA) has been identified as being different to the rest of Australia in terms of rainfall patterns. However, rainfall patterns within the ESA itself are not well understood. This study identifies Australian rainfall districts that exhibit similar (and different) temporal variation, with the primary aim being to determine if the ESA can be considered a homogenous region with respect to rainfall. The results (a) confirm that the ESA is different to the rest of Australia and (b) show that the ESA is not homogenous and that East Coast Lows (ECLs) are linked to this inhomogeneity. For winter (JJA) three separate divisions within the ESA are identified and at least two clear divisions are identified in other seasons. ECL sub-types contribute to this inhomogeneity because each ECL sub-type is associated with different spatio-temporal rainfall patterns across the ESA. This is an important insight for natural resources management and emergency services within the heavily populated ESA because it demonstrates that existing climate related risks are different across the ESA. Further, the way climate risks change in the future is also likely to be inconsistent across the ESA. Future climate related risks will depend on how ECL behaviour (e.g., intensity, frequency, location, duration, path and geographical extent) changes. This reinforces the need for locally relevant and practically useful climate science information and adaptation strategies¿as opposed to the State- or country-wide information and adaptation approaches that are commonly used.

Study region: Kathmandu Valley, Nepal. Study focus: Water scarcity affects more than 40 % of the global population. Households in low- and middle-income countries typically use alternative water sources to piped water such as groundwater, tanker water and jar water and various coping strategies to deal with water scarcity. This study quantitatively examines the association between using multiple water sources and individual water consumption. In addition, we investigated the relationship between individual water consumption and physical (i.e. water source, supply time) and non-physical (wealth status, education for household head, house ownership, participation in local community, water treatment) factors before and after the 2015 Gorkha earthquake. A survey about socio-demographics, domestic water use behavior, and community involvement was conducted three times and the data collected from 992 households were used for analysis. New hydrological insights for the region: It was confirmed that use of additional water sources is associated with greater individual water consumption. This was especially the case in households using both groundwater and tanker water. In addition, wealth status, education for household head, and house ownership were associated with increased individual water consumption but this association was not apparent after the earthquake. Participation in the local community was also associated with increased individual water consumption except for the period impacted by the earthquake. Households using treated water consumed less water across all periods surveyed.

An important step in developing climate forecasts is the identification of an appropriate set of predictors. Seasonal rainfall forecasts for South Australia (SA) currently have low predictive skill. It is hypothesised that this is because the large-scale climate processes influencing SA's rainfall variability have yet to be completely identified and therefore are not adequately represented in forecast models. Here, relationships between large-scale climate influences and rainfall in SA are assessed with a focus on methods that account for non-linearities inherent in the climate system. A threshold method and also a novel method for climate predictor selection, Partial Mutual Information, are used to establish the hierarchy of importance of the key influences. From a large suite of potential predictors, variability in the Subtropical Ridge intensity, blocking and the gradient of sea surface temperatures (SSTs) in the tropical central and eastern Indian Ocean are found to be key indicators of seasonal rainfall variability in SA. Interactions between processes are shown to increase the amount of variability accounted for and therefore need to be better considered when producing seasonal forecasts. Notably, the view of which climate process(es) is(are) important changes depending on the input variables used, suggesting that it is not wise to make a priori assumptions about what is or is not important. Furthermore, even a perfect forecast of El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD), the focus of forecasting efforts in Australia, will not necessarily lead to an improvement to forecast skill in SA given that these processes are not key for the region. The results of this analysis can inform the development of existing and new statistical and dynamical seasonal forecasting systems for SA, and for other regions where the impacts of climate variability are significant but not necessarily dominated by ENSO and IOD.

Recent efforts to understand tropical cyclone (TC) activity in the southwest Pacific (SWP) have led to the development of numerous TC databases. The methods used to compile each database vary and are based on data from different meteorological centres, standalone TC databases and archived synoptic charts. Therefore the aims of this study are to (i) provide a spatiooral comparison of three TC best-track (BT) databases and explore any differences between them (and any associated implications) and (ii) investigate whether there are any spatial, temporal or statistical differences between pre-satellite (1945-1969), postsatellite (1970-2011) and post-geostationary satellite (1982-2011) era TC data given the changing observational technologies with time. To achieve this, we compare three besttrack TC databases for the SWP region (0-35° S, 135° E-120° W) from 1945 to 2011: the Joint TyphoonWarning Center (JTWC), the International Best Track Archive for Climate Stewardship (IBTrACS) and the Southwest Pacific Enhanced Archive of Tropical Cyclones (SPEArTC). The results of this study suggest that SPEArTC is the most complete repository of TCs for the SWP region. In particular, we show that the SPEArTC database includes a number of additional TCs, not included in either the JTWC or IBTrACS database. These SPEArTC events do occur under environmental conditions conducive to tropical cyclogenesis (TC genesis), including anomalously negative 700 hPa vorticity (VORT), anomalously negative vertical shear of zonal winds (VSZW), anomalously negative 700 hPa geopotential height (GPH), cyclonic (absolute) 700 hPa winds and low values of absolute vertical wind shear (EVWS). Further, while changes in observational technologies from 1945 have undoubtedly improved our ability to detect and monitor TCs, we show that the number of TCs detected prior to the satellite era (1945-1969) are not statistically different to those in the postsatellite era (post-1970). Although data from pre-satellite and pre-geostationary satellite periods are currently inadequate for investigating TC intensity, this study suggests that SPEArTC data (from 1945) may be used to investigate longterm variability of TC counts and TC genesis locations.

Floods are caused by a number of interacting factors, making it remarkably difficult to explain changes in flood hazard. This paper reviews the current understanding of historical trends and variability in flood hazard across Australia. Links between flood and rainfall trends cannot be made due to the influence of climate processes over a number of spatial and temporal scales as well as landscape changes that affect the catchment response. There are also still considerable uncertainties in future rainfall projections, particularly for sub-daily extreme rainfall events. This is in addition to the inherent uncertainty in hydrological modelling such as antecedent conditions and feedback mechanisms. Research questions are posed based on the current state of knowledge. These include a need for high-resolution climate modelling studies and efforts in compiling and analysing databases of sub-daily rainfall and flood records. Finally there is a need to develop modelling frameworks that can deal with the interaction between climate processes at different spatio-temporal scales, so that historical flood trends can be better explained and future flood behaviour understood.

Paleoclimate research indicates that the Australian instrumental climate record (~100 years) does not cover the full range of hydroclimatic variability that is possible. To better understand the implications of this on catchment-scale water resources management, a 1013-year (1000-2012 common era (CE)) annual rainfall reconstruction was produced for the Williams River catchment in coastal eastern Australia. No high-resolution paleoclimate proxies are located in the region and so a teleconnection between summer sea salt deposition recorded in ice cores from East Antarctica and rainfall variability in eastern Australia was exploited to reconstruct the catchment-scale rainfall record. The reconstruction shows that significantly longer and more frequent wet and dry periods were experienced in the preinstrumental compared to the instrumental period. This suggests that existing drought and flood risk assessments underestimate the true risks due to the reliance on data and statistics obtained from only the instrumental record. This raises questions about the robustness of existing water security and flood protection measures and has serious implications for water resources management, infrastructure design and catchment planning. The method used in this proof of concept study is transferable and enables similar insights into the true risk of flood/drought to be gained for other paleoclimate proxy poor regions for which suitable remote teleconnected proxies exist. This will lead to improved understanding and ability to deal with the impacts of multi-decadal to centennial hydroclimatic variability.

The destruction caused by tropical cyclone (TC) Pam in March 2015 is considered one of the worst natural disasters in the history of Vanuatu. It has highlighted the need for a better understanding of TC impacts and adaptation in the Southwest Pacific (SWP) region. Therefore, the key aims of this study are to (i) understand local perceptions of TC activity, (ii) investigate impacts of TC activity and (iii) uncover adaptation strategies used to offset the impacts of TCs. To address these aims, a survey (with 130 participants from urban areas) was conducted across three SWP small island states (SISs): Fiji, Vanuatu and Tonga (FVT). It was found that respondents generally had a high level of risk perception and awareness of TCs and the associated physical impacts, but lacked an understanding of the underlying weather conditions. Responses highlighted that current methods of adaptation generally occur at the local level, immediately prior to a TC event (preparation of property, gathering of food, finding a safe place to shelter). However higher level adaptation measures (such as the modification to building structures) may reduce vulnerability further. Finally, we discuss the potential of utilising weather-related traditional knowledge and non-traditional knowledge of empirical and climate-model-based weather forecasts to improve TC outlooks, which would ultimately reduce vulnerability and increase adaptive capacity. Importantly, lessons learned from this study may result in the modification and/or development of existing adaptation strategies.

Droughts are a recurrent and natural part of the Australian hydroclimate, with evidence of drought dating back thousands of years. However, our ability to monitor, attribute, forecast and manage drought is exposed as insufficient whenever a drought occurs. This paper summarises what is known about drought hazard, as opposed to the impacts of drought, in Australia and finds that, unlike other hydroclimatic hazards, we currently have very limited ability to tell when a drought will begin or end. Understanding, defining, monitoring, forecasting and managing drought is also complex due to the variety of temporal and spatial scales at which drought occurs and the diverse direct and indirect causes and consequences of drought. We argue that to improve understanding and management of drought, three key research challenges should be targeted: (1) defining and monitoring drought characteristics (i.e. frequency, start, duration, magnitude, and spatial extent) to remove confusion between drought causes, impacts and risks and better distinguish between drought, aridity, and water scarcity due to over-extractions; (2) documenting historical (instrumental and pre-instrumental) variation in drought to better understand baseline drought characteristics, enable more rigorous identification and attribution of drought events or trends, inform/evaluate hydrological and climate modelling activities and give insights into possible future drought scenarios; (3) improving the prediction and projection of drought characteristics with seasonal to multidecadal lead times and including more realistic modelling of the multiple factors that cause (or contribute to) drought so that the impacts of natural variability and anthropogenic climate change are accounted for and the reliability of long-term drought projections increases.

This study identifies the severity of impacts of drought in 2012 on domestic water supply, crop production, unskilled rural employment, and financial status of rural households in a drought-prone area of India. It is based on secondary and primary data collected by interviewing 223 households. The data were analyzed using descriptive and inferential applications in SPSS. As a consequence of drought, access to domestic water supply was cumbersome and time spent on water collection activities almost doubled compared with the time required in years with normal rainfall. On average, a respondent household suffered a loss of about 86% in production of major crops. High reductions in on-farm unskilled employment opportunities and an increase in unskilled labor in off-farm rural employment activities were reported. It was found that about 69% of respondents were availing loans and 79% of them delayed repayment of loans due to the consequences of drought. Our results indicated that the extent of drought damage varied according to household size, annual income, landholding size, farming system in use, and drought intensity. The effects of these factors on farming communities are reported with empirical evidence. Respondents with large family size, low to marginal land holding size, low income, and rainfed farming systems are found to be more vulnerable to drought impacts; special attention should be given towards increasing their resilience when designing drought management strategies.

Rainfall intensity-frequency-duration (IFD) relationships are commonly required for the design and planning of water supply and management systems around the world. Currently, IFD information is based on the "stationary climate assumption" that weather at any point in time will vary randomly and that the underlying climate statistics (including both averages and extremes) will remain constant irrespective of the period of record. However, the validity of this assumption has been questioned over the last 15 years, particularly in Australia, following an improved understanding of the significant impact of climate variability and change occurring on interannual to multidecadal timescales. This paper provides evidence of regime shifts in annual maximum rainfall time series (between 1913-2010) using 96 daily rainfall stations and 66 sub-daily rainfall stations across Australia. Furthermore, the effect of these regime shifts on the resulting IFD estimates are explored for three long-term (1913-2010) sub-daily rainfall records (Brisbane, Sydney, and Melbourne) utilizing insights into multidecadal climate variability. It is demonstrated that IFD relationships may under-or over-estimate the design rainfall depending on the length and time period spanned by the rainfall data used to develop the IFD information. It is recommended that regime shifts in annual maximum rainfall be explicitly considered and appropriately treated in the ongoing revisions of the Engineers Australia guide to estimating and utilizing IFD information, Australian Rainfall and Runoff (ARR), and that clear guidance needs to be provided on how to deal with the issue of regime shifts in extreme events (irrespective of whether this is due to natural or anthropogenic climate change). The findings of our study also have important implications for other regions of the world that exhibit considerable hydroclimatic variability and where IFD information is based on relatively short data sets.

The Interdecadal Pacific Oscillation (IPO) influences multidecadal drought risk across the Pacific, but there are no millennial-length, high-resolution IPO reconstructions for quantifying long-term drought risk. In Australia, drought risk increases in positive phases of the IPO, yet few suitable rainfall proxies and short (~100 years) instrumental records mean large uncertainties remain around drought frequency and duration. Likewise, it is unknown whether megadroughts have occurred in Australia's past. In this study, an atmospheric teleconnection in the Indian Ocean midlatitudes linking East Antarctica and Australia is exploited to produce the first accurate, annually dated millennial-length IPO reconstruction from the Law Dome (East Antarctica) ice core. Combined with an eastern Australian rainfall proxy from Law Dome, the first millennial-length Australian megadrought (>5 year duration) reconstruction is presented. Eight megadroughts are identified including one 39 year drought (A.D. 1174-1212), which occurred during an unprecedented century of aridity (A.D. 1102-1212).

Recurring drought is a major challenge in the Drought Prone Area of Maharashtra State in India. Agriculture (e.g., rainfed cropping and livestock) is the major income activity of over 64% of the state's population. The objective of this study is to understand the rural farming community's perception of drought impacts on their socio-economic activities and environment, their adaptation at the household level and opinions on government drought mitigation measures. This study is based on both secondary and primary data collected via a survey of 223 farming households. The results show that decrease in yield of cereals, horticultural crops, livestock production and loss of employment, all associated with decreased income of farmers, were the most immediate economic impacts of drought. Social impacts such as population migration, impacts on health and schooling of children, hopelessness and sense of loss, conflicts in society for water, and malnutrition due to changed food preferences were also reported. The environmental impacts such as increases in average atmospheric temperature, pasture-forest degradation, deteriorated water quality, damage to fish habitat-wild life, and groundwater depletion were perceived by farmers to high extent. In spite of good perception of severity of drought impacts by farmers and their familiarity with various adaptation options, the preference given for their adoption in agriculture was not good enough. Also to mitigate drought, the government provided various mitigation measures, but the level of satisfaction amongst farmers was low. It is expected that this study will help policy makers to develop more appropriate drought adaptation policies in India.

There is a recognised gap between what climate science can currently provide and what end users of that information require to make robust adaptation decisions about their climate-related risks. This issue has been identified as a major barrier to successful climate change adaptation outcomes and is emphasised within the water resource management and agricultural sectors because of high uncertainty surrounding precipitation projections. This paper details the outcomes of a survey and workshop aimed at better understanding this gap. To bridge the gap, it is recommended that communication and packaging of climate information be improved via a formalised 'knowledge broker'. It is also suggested that a 'terms of reference' for key climate change-related terms be developed and agreed upon by both climate science providers and end users to reduce the misuse of terminology and subsequent confusion. Further, it is recommended that additional research be conducted into natural variability and baseline risk to provide a realistic background on which climate change projections and associated uncertainties are assessed. Finally, for successful climate change adaptation, new tools and methods are needed that deal explicitly with end user needs and the practical limitations end users face (e.g. time, funding, human resources, politics) when attempting to make robust decisions under climate change-related uncertainty.

A shift in climate occurred during the mid-1970s that affected the hydroclimate of the Southern Hemisphere resulting in drying trends across continental regions including Australia, New Zealand and southern and western Africa. There is also anecdotal evidence of other periods of climatic synchronicity in the Southern Hemisphere (e.g., the 1920s and 1940s), indicating that the mid-1970s event may not be anomalous. This paper identifies periods within the last ~120 years using statistical analysis where dry spells (in terms of annual to multi-decadal rainfall deficiencies) have coincided across the continental Southern Hemisphere in order to characterize temporal consistency. It is shown that synchronicity of dry spells is (a) most likely common over the last 120 years and (b) associated with changes in the large-scale climate modes of the Pacific, Indian and Southern Oceans. Importantly, the findings presented in this paper have marked implications for drought management and drought forecasting studies in the Southern Hemisphere. © Author(s) 2014.

Southeast Australia (SEA) experienced a protracted drought during the mid-1990s until early 2010 (known as the Big Dry or Millennium Drought) that resulted in serious environmental, social and economic effects. This paper analyses a range of historical climate data sets to place the recent drought into context in terms of Southern Hemisphere inter-annual to multi-decadal hydroclimatic variability. The findings indicate that the recent Big Dry in SEA is in fact linked to the widespread Southern Hemisphere climate shift towards drier conditions that began in the mid-1970s. However, it is shown that this link is masked because the large-scale climate drivers responsible for drying in other regions of the mid-latitudes since the mid-1970s did not have the same effect on SEA during the mid-to late 1980s and early 1990s. More specifically, smaller-scale synoptic processes resulted in elevated autumn and winter rainfall (a crucial period for SEA hydrology) during the mid-to late 1980s and early 1990s, which punctuated the longer-term drying. From the mid-1990s to 2010 the frequency of the synoptic processes associated with elevated autumn/winter rainfall decreased, resulting in a return to drier than average conditions and the onset of the Big Dry. The findings presented in this paper have marked implications for water management and climate attribution studies in SEA, in particular for understanding and dealing with "baseline" (i.e. current) hydroclimatic risks. © 2014 Author(s).

Urban bulk water systems supply water with high reliability and, in the event of extreme drought, must avoid catastrophic economic and social collapse. In view of the deep uncertainty about future climate change, it is vital that robust solutions be found that secure urban bulk water systems against extreme drought. To tackle this challenge an approach was developed integrating: 1) a stochastic model of multi-site streamflow conditioned on future climate change scenarios; 2) Monte Carlo simulation of the urban bulk water system incorporated into a robust optimization framework and solved using a multi-objective evolutionary algorithm; and 3) a comprehensive decision space including operating rules, investment in new sources and source substitution and a drought contingency plan with multiple actions with increasingly severe economic and social impact. A case study demonstrated the feasibility of this approach for a complex urban bulk water supply system. The primary objective was to minimize the expected present worth cost arising from infrastructure investment, system operation and the social cost of "normal" and emergency restrictions. By introducing a second objective which minimizes either the difference in present worth cost between the driest and wettest future climate change scenarios or the present worth cost for driest climate scenario, the trade-off between efficiency and robustness was identified. The results show that a significant change in investment and operating strategy can occur when the decision maker expresses a stronger preference for robustness and that this depends on the adopted robustness measure. Moreover, solutions are not only impacted by the degree of uncertainty about future climate change but also by the stress imposed on the system and the range of available options.

© 2015, Engineers Australia. All rights reserved.East Coast Lows (ECLs) are intense low-pressure systems which occur over the subtropical east coasts of Southern Hemisphere continents, including Australia. These systems are typically associated with gale-force winds, large seas, storm surges, heavy rainfall and flooding. While these ECL impacts are mostly negative the rainfall associated with ECLs is also very important for urban water security within the heavily populated eastern seaboard of Australian (ESA). This study examines historical ECLs to gain insights into the timing, frequency and location of ECL occurrence as well as the magnitude and spatial extent of ECL impacts on rainfall. The different characteristics and impacts associated with the different ECL sub-types are highlighted and it is demonstrated how this information can be used to stochastically simulate daily rainfall such that the statistics important for catchment scale hydrology (e.g. clustering of extreme events, long-term persistence, frequency/duration/magnitude of wet and dry spells etc.) are realistically preserved. These simulated rainfall sequences, that incorporate the spatial and temporal hydroclimatic variability caused by ECLs and other climate phenomena, are important inputs into hydrological models used to determine current and future urban water security.

This study investigates the frequency and timing of six types of East Coast Lows (ECL) as well as their impact on rainfall along the Queensland and New South Wales coastline. By analysing the data from the Bureau of Meteorology's (BoM) NSW Maritime Lows database (1970-2006) as well as observed daily rainfall data from 27 BoM stations along the east coast, the relative importance of each type of ECL and their regions of preferential impact is quantified. This preliminary work was then repeated and expanded via utilisation of the BoMs recently updated ECL database: Maps and Tables of Climate Hazards of the Eastern Seaboard (MATCHES). MATCHES is a tool that identifies significant rainfall/wind/wave/water-level events on the Eastern Seaboard according to user specified thresholds while simultaneously displaying east coast low (ECL) tracks. This allows easy analysis of the relationship between the movement and location of an ECL and where its impacts are subsequently felt. Results suggest that the average timing of 5 of the 6 East Coast Low types (i.e. all except extropical cyclones) are converging around late autumn and early winter, whilst ex-tropical cyclones are occurring earlier, toward the middle of summer. Interannual rainfall totals are found to vary with that contributed by ECLs while the spatial distributions of daily rainfall attributed to the different types of systems were consistent with their associated area of formation. In conjunction with the cyclical nature of ECL frequency, the implications these results have on the distribution of rainfall, extreme events and water security along the densely populated east Australian seaboard are discussed.